It might even have a thin enough atmosphere to not completely crush a human.

If the gravity isn't too high, we can engineer around all the rest. Ought to be just fine for bots if the solder doesn't flow at its temps. A giant pot of natural resources at 11LY is very exciting for colonials!

A few companies, such as Planetary Resources and Deep Space Industries, have formed with the goal of mining asteroids. Why asteroids? Because it currently costs several thousand dollars per pound to put anything from Earth into low-earth orbit. Asteroids are probably made of all the ingredients necessary to live in space, including water. These companies intend to supply the raw materials to support an entirely new space economy.

Sounds preposterous, I know, but it's almost certainly easier than colonizing the first completely habitable earth-like exoplanet (and the article actually makes it sound more plausible than the name implies). That's not to say we should stop looking for them, of course...far from it. Those are the best chance we have to find extraterrestrial life, intelligent or otherwise.

As a larger planet, however, since force of gravity is inversely proportional to the square of the distance, the surface gravity of a world otherwise equivalent in density to another ends up rises linearly with the diameter of the planet. If it is of similar composition to earth, then 5.4 earth masses would make it cbrt(5.4) times the size of earth, or roughly 1.75g at the planet's surface. Assuming that the atmospheric density is comparable to earth's (possible, even with greater gravity if the atmosphere itself is proportionally thinner), then this is theoretically survivable by human beings for short periods, or even prolonged ones if they were able to acclimate to the increased gravitation pull gradually, over a span of several years, giving time for skeletal tissue to build up and strengthen the body's structure to survive the increased tension.

But, of course, we don't know that the density of the planet is comparable to earth.

It is probably less. Of all the planets and spherical moons is our solar system, no other has a density as high as Earth. Earth's density is 5.5 gm/cc. The moon is 3.3. Mars is 3.9. If this planet has a density similar to the moon, its surface gravity would be about the same as Earth's.

If the surface gravity were about the same as the Earth's, wouldn't that mean that its atmospheric pressure at the surface would be about the same also. After all, it's gravity holding the gas down, and technically the atmospheric pressure is the weight of the gas above that point. Assuming the gas is trapped to the planet by the gravity, then you might have about the same amount of gas trapped above a point by a similar amount of gravity.

If the surface gravity were about the same as the Earth's, wouldn't that mean that its atmospheric pressure at the surface would be about the same also. After all, it's gravity holding the gas down, and technically the atmospheric pressure is the weight of the gas above that point. Assuming the gas is trapped to the planet by the gravity, then you might have about the same amount of gas trapped above a point by a similar amount of gravity.

I'm just speculating though.

No. Atmospheric pressure is not simply a function of gravity. It is more a function of how much stuff there is in the atmosphere.

Okay, but for example:I am pretty overweight, but I'm in pretty good physical condition. I currently weigh 180 lbs. On this planet, I would weigh 315 lbs. That's like carrying 135 lbs of extra weight. If I'm backpacking, I carry anywhere from 25-35 lbs total, and I can "go" all day like that. I get pretty wiped out, but it's something I can adjust to, over time. I've hiked at 70 lbs, carrying equipment for other "less capable" people. That's really about my limit. This seriously cuts my hike range f

*YOU* might not... but your great-great or great-great-great grandchildren might... I am presuming that you'd be living on a generational spaceship where the gravity can be slowly modified so that by the time they arrive, they would be fully acclimated to the higher gravity.

I'd think the question would be, if we can create a generational spaceship, what's the purpose of creating a colony on a planet we'd have troubles adapting to? Instead we'd just build an orbiting space station around the planet and mine it using robots.

As a larger planet, however, since force of gravity is inversely proportional to the square of the distance, the surface gravity of a world otherwise equivalent in density to another ends up rises linearly with the diameter of the planet. If it is of similar composition to earth, then 5.4 earth masses would make it cbrt(5.4) times the size of earth, or roughly 1.75g at the planet's surface.

Doesn't that assume that the source of the gravity is a point at the center of a planet? Is that how planetary gravity actually works in practice?

If you assume any sort of liquid core during the planet's history, then the heaviest masses would move toward equilibrium. That would tend to be at the center, since moving away from the center would usually be moving against more mass (and more gravity) than what it would be moving toward.

so t = 3.3 years to half way. 6.6 years to go all the way and thus 13.2 years for the round trip.

Thus you could easily go there and come back in your lifetime.

Note that this is also Faster than light can make the round trip. However that is not any violation of relativity. THe people on earth would have aged a lot more than 13.3 years during your trip. But you would only have aged 13.3 years.

it's a matter of fuel with sufficient thrust to weight ratio (unless you want to start thinking about using the interstellar gases as the propellant--- that get's dicey because they will be approaching your craft at near the speed of light)

Let's see if I can work this out correctly;First assume the spaceships weight negligibly different than the mass of the fuel. The thrust needed to push the weight at a steady 1g will be proportional to the mass of the ship at each interval of time. SO the rate of mass burn is proportional to the mass which means the mass is a decaying exponential.

M = Mo * exp( -g * time / thrust_to_weight )

If you think about this for a moment it becomes clear that any amount of mass would do since as the mass gets lighter it takes less fuel so the ship could go indefinitely at 1g. The problem is the assumption that the ship weighs nothing. so let's fix that.

dM/dt = -g*(M+Ms)/thrust_to_weight.

where Ms = mass of ship and M = mass of fuel.

I'm spacing on how to solve that equation so I'll approximate it by saying that until M = Ms we can mostly ignore the ship mass. therfore for a 6.6 year flight time the fuel required is about:

Mfuel = Ms * exp( g* (6.6 years)/thrust_to_weight )

Mfule = Ms * exp( +303,800,000/thrust_to_weight).

So you need a rather high thrust to weight ratio due to the coefficient in the exponetial.

Compared to the amount of chemical fuel needed to get large spacecraft out of earth orbit, that is peanuts.

Remember, nothing says the ship must be built on and launch from Earth. Build it out by the asteroid belt, mine them for material, start the ship moving and time it to slingshot around Jupiter or Saturn, and use your engine of choice for the journey.

True. Finding interesting destinations and developing new propulsion methods are mutually complementary tasks. Both are important and can be done in parallel by people with different talents and interests.

No you don't - just turn off the rockets and let it fall half way there (accelerating) under the other planets gravity, then turn around so that you slow down at the rate of earth's gravity pulling you back for the second half of the trip. All you need is the fuel to get to orbit and you're practically done.

1. we don't have the technology to achieve that. 2. without some as yet to be thought of technology, the relativistic relative motion of the incident protons, even at 1 per cubic meter or so, would interact with the vehicle structure and create showers of particles, killing the crew.

Something I've wondered about is why we don't see more relativistic protons hitting earth or the ISS. Is the relative velocity of everything in the universe extremely low? I don't think so. So where are these missing showers on earth right now?

first of all, any high energy protons that come into the region around Earth are deflected by our magnetosphere. At worse, nothing happens. At best, you get pretty lights in the northern sky. Second, the particles aren't necessarily travelling at relativistic speeds, you are (when travelling at velocities approaching c). From your perspective, you're in a sea of relativistic protons even if they're standing still.

Try plugging your trip into the Tsiolkovsky rocket equation [wolframalpha.com]. Assume the most theoretically advanced engine exhaust velocity. What is the required initial mass for your rocket? How many multiples of the mass of the entire universe are required for your rocket?

Before embarking to such a trip you had better wait the confirmation of a planet around Alpha Centauri at 4.3 ly. Even if the already announced discovery turns out to be wrong, the probability that some planets exist in the Alpha Centauri system is large.

people are forgetting that no one's going to be awake or likely aging during this flight. suspended animation will be required for a trip like this and likely possible in the not too distant future (100 yrs?).

so it doesn't really matter so much if it takes 13.3 yrs or 100 yrs.

the hardest part will be that people don't do well at funding and executing projects that last more than a life time. the organizations and countries and people that launch these missions will be long gone by the time the crew arrives.

You're talking speed, while Parent was talking acceleration. A ship to LEO takes about ten minutes to achieve orbital velocity, then no thrust after that. A ship to Leo (any star therein) could actually get there in a reasonable amount of time if 1G of acceleration could be maintained all the way to the midpoint of the journey and then kept up as deceleration the rest of the way. The big catch is the number of stars worth of fuel you would have to bring with you.

You seem to completely not understand the subject, which makes us wonder why you are posting.

"Us?" Do you have a turd in your pocket? Is Slashdot only for people who are 100% knowledgeable in all given subjects?

Snark aside, I read the original equation wrong. I didn't realize that the reason that the second half of travel was as long as the first half was because of constant acceleration switching directions. But that doesn't mean you need to be a dick about it. But, by all means, don't let me stop you from explaining how one would travel a linear distance of 11 light years in 6.6 years.

This was the topic of "How the Universe Works" last night. Even if we figured out the propulsion system (fusion or anti-matter), and figured out a good way to maintain artificial gravity, we would still face the issue of being exposed to large doses of radiation. A simple coating to absorb the radiation wouldn't work because it emits the absorbed radiation in another form, which is still harmful. We would need some type of magnetic shielding similar to how the Earth is currently protected. They said tha

5.4 solar masses is m sin i, where i is the inclination of the orbit to the plane of the sky. Therefore, the mass could well be greater than 5.4 solar masses, and so it could be a neptune or in rare cases of close to face-on inclination have even higher mass.

This is a limitation of the radial velocity method, which was used in this detection; with transits (where you watch the star dim as the planet passes in front of it) you already know the inclination---it's 90 degrees to a high accuracy. So you know the

Oh.. it's just 11 light years away. That's a small number, right? As much as I'd like to be able to say we have a "warp drive" or "jump drive" or something like that... at the moment 11 light years might as well be 11 million light years. it makes no difference to our ability to get there.

If we're being fanciful, then we could just as easily say "it took humans 4 billion years and change to colonize the Western Hemisphere of planet Earth. The fact that they didn't for most of that is irrelevant." Or substitute 13 billion years instead and say "the fact that neither existed for most of that is irrelevant." The fact still remains that in cosmological terms, things have been around for a really, really, really long time in comparison to the minute instant that we as a species have existed, let

Nope. Not the western hemisphere, but rather the eastern. Humans came from Africa, which is in the half of the globe that has eastern longitude. From there, they spread to Asia and Europe, and from Asia to the Americas, the latter movement having been a rather recent event in human history ( less than 100.000 years ago ).

Oh.. it's just 11 light years away. That's a small number, right? As much as I'd like to be able to say we have a "warp drive" or "jump drive" or something like that... at the moment 11 light years might as well be 11 million light years. it makes no difference to our ability to get there.

Exactly. Even if we DID build an Orion nuclear spacecraft (http://www.spacedaily.com/news/nuclearspace-03h.html), at best we'll get 1/10th light speed, and it would take the equivalent of several thousand Saturn V launches to build the ship in space. So we're talking at best a 220 year round trip, IF everything went right.

Building an Orion could very well bankrupt the nation that attempts it. It would be obscenely expensive; and, while it is the best our current technology could produce, it would be a hideously inefficient way to go about travelling between stars.

Exactly. Currently, our furthest space probe is Voyager 1 and that's only 0.002 light years away from us after travelling for 37 years. At that rate, it will take 18,500 years before it travels one light year and over 200,000 years before it travels 11 light years. Even if we could leave right now and cut the travel time in half, we still wouldn't arrive until the year 102,014. To put it another way, we as a species (Homo Sapiens) have only been around for 200,000 years. A probe sent to this closest pl

At one point, the prevailing scientific theory was that planets were a rarity. Then we found the first exoplanet and astronomers started wondering if they might be more common. By now, with the thousands of exoplanets found, we know that planets are plentiful. We don't know how many Earth-like ones are out there, but many astronomers think that this is more of a deficiency in our planetary detection methods than a rarity of Earth-like worlds. (Bigger planets are easier to detect.)

That still doesn't explain why they would think planets were uncommon. We didn't know of any extra solar planets because we didn't have instruments that could find them...and we knew they were inadequate. Just because we were incapable of seeing them, that's no reason to believe they were uncommon. What we can infer from the known laws of physics suggests that all you need is gravity and matter and you're going to get clumps of matter orbiting other clumps matter orbiting other clumps of matter until you

You'd need to talk to an astronomer to find out the reason that astronomers at the time thought planets weren't common. It might have just been because we hadn't detected any and a lack of evidence for something translates into a certain amount of skepticism about whether that thing exists.`